The disclosure is directed to systems and methods for direct clean-in-place (CIP) of inkjet print heads. Specifically, the disclosure is directed to systems and methods allowing CIP of print heads by selectably alternating the position of a mask between printing, cleaning and purging positions.
Inkjet printing heads require periodic cleaning of printing nozzles to remove buildup (solid sediments) on the nozzles, remove air bubbles, and otherwise maintain printing quality. Cleaning the printing head is a significant part of the inkjet printing process, for example in some industrial settings the printing head is cleaned as often as every two minutes. The frequency of cleaning depends on the specific application for which the printing head is being used. Typically, cleaning can also be done by removing the print head to one side of the printer for easy access and manually cleaning the head. These methods are time consuming and inefficient.
An orifice plate, can be located on the printing side (lower surface) of the printing head, providing access for the nozzles to print, while potentially also providing protection for the printing head. Jetted ink from each nozzle can exits the orifice for printing. During periodic cleaning and/or after purging, the orifice surface can be cleaned to remove buildup, purged liquid, and enable proper jetting of the printing liquid from the nozzles (via the orifices). In order to preserve the smoothness and high interfacial tension between the printing side and the jetted ink (non-wetting characteristic) and the orifice surface, care must be taken in performing wiping.
Typically, removing content without contact to the orifice plate can be done using vacuum where a vacuum ‘head’ is moved across the orifice plate. The vacuum head can be maneuvered sufficiently close to allow the vacuum induced suction, to remove the jetted liquid from the orifice plate. Because the vacuum head does not contact the orifice plate, efficiency of the orifice plate cleaning is low. Typically, where an injection bath is present, the print head move to one side of the printer to purge the ink, which is time consuming and otherwise inefficient. Other disadvantages to conventional vacuum removal include cost, printing speed, reliability, and quality.
Moreover, when the ink contains volatile components, the ink at a tip of a nozzle may lose those components, resulting in certain circumstances in the remaining ingredients of the ink forming a semi-solid skin at the nozzle tip. The semi-solid skin, or buildup of solid sediments, can interfere with the jetting of ink from the nozzles, reducing the quality or even disabling jetting of ink from one or more nozzles. As the nozzle tips are aligned with orifices in an orifice plate, sediment buildup can also be on the orifices and/or orifice plate.
There is therefore a need for a system for cleaning an orifice plate, with increased efficiency over conventional techniques, and preventing sediment buildup.